1. Field of the Invention
The invention generally relates to electric systems and devices that generate and accumulate charge for application to living beings. More specifically, the invention relates to electric disabling devices commonly referred to as stun-guns, stun-batons or the like for delivering an incapacitating, but less than lethal, sequence of electric shocks to a person.
2. Background Information
Hand-held stun-guns are widely used by police officers to subdue uncooperative or potentially dangerous individuals by subjecting them to electric current pulses inducing incapacitating muscle cramps. The jolt from a stun gun is intended to cause such severe cramping as to prohibit locomotion and to cause the victim to fall to the ground. Generally speaking, there are two limiting concerns in delivering an incapacitating electric shock. At one extreme, if too little energy is delivered to a targeted individual, he or she may not be incapacitated and may be able to persist in an attack on a police office. On the other hand, if extremely large electrical currents are delivered, the shock may be lethal, rather than merely incapacitating.
Prior art stun guns operate by charging a capacitor to a relatively high voltage and then discharging the capacitor through the primary winding of a step-up transformer so as to produce a much higher voltage on electrodes propelled toward a target. If the electrodes are not in intimate contact with the target, voltages on the order of 50-60 kV need to be supplied to the electrodes to ionize the air between the electrodes and the target to establish a current path. Once contact has been established lower voltages, on the order of hundreds to a few thousand volts, are adequate for sending disabling current pulses through the target.
In a typical prior art stun gun the capacitive discharge is controlled by a gas discharge tube. The capacitor is charged from a relatively high voltage power supply until the voltage across its terminals is high enough to trigger breakdown in the gas discharge tube, and to cause the gas discharge tube to switch from its initial non-conducting state to a highly conductive state in which the capacitor is electrically connected to the transformer. The capacitor then discharges through the primary winding of the transformer until its voltage falls below the minimum voltage at which the gas discharge tube will conduct. The gas discharge tube then switches to its original high resistance state and the cycle can be repeated. In this arrangement the pulse duration, repetition rate, output voltage, etc. are determined by component selection. That is, one can select gas discharge tubes with different turn-on and turn-off voltages, but once the turn-on voltage is attained, the device will conduct until the voltage falls below the turn-off level.
Physiological studies of the effects of electrical impulses on nerves that control skeletal muscles indicate that a pulse needs to last longer than about 150 microseconds to be efficient at ‘firing’ the nerve tissue, which is critical for causing cramping or immobilization. Once stimulated, the nerve tissue requires four milliseconds or more to recover.